Hello Health Rounds readers! Moderna has run into recent U.S. regulatory roadblocks with its vaccines using mRNA technology, but today we highlight data showing its experimental combination flu/COVID-19 shot appears to work well. We also report on a study in mice that could shed light on why some people without celiac disease may still be sensitive to gluten. 

In other news: US health regulators to consider safety of processed ingredients; UK eyes curbs on social media, chatbots; Medical groups urge US judge to block vaccine policy shifts under RFK Jr; WHO prequalifies new polio vaccine; and FDA's Makary backs measles vaccines as cases in South Carolina rise to 962.

Moderna is looking for growth overseas after the U.S. FDA refused to review its experimental flu shot and the country's top health officials have deprioritized vaccination.

A two-in-one mRNA vaccine developed by Moderna that targets  seasonal influenza and COVID-19 produced robust and durable immune responses without safety concerns in a small mid-stage trial, the company reported.

The experimental vaccine simultaneously includes messenger RNA instructions for the body to build copies of proteins from flu strains and from the original COVID-19 virus, so the immune system can learn to recognize and attack them.

The study involved 550 healthy U.S. adults ages 18 to 75 who received either the experimental combo vaccine and a placebo or two separate shots of Moderna’s commercially available mRNA flu and COVID vaccines, according to a report published in Human Vaccines and Therapeutics. 

“A single dose of mRNA-1073 elicited durable immune responses through six months against all vaccine-matched influenza and SARS-CoV-2 strains,” they reported, using the current designation for the combo vaccine.

The results support continuing evaluations of mRNA-based multi-component vaccines that simultaneously protect against seasonal influenza and COVID-19 in a single dose, the researchers concluded.

Moderna this month said it was looking for revenue growth outside the U.S. given the current U.S. administration's antipathy toward mRNA technology. The Department of Health and Human Services run by long-time anti-vaccine activist Robert F. Kennedy Jr. canceled a $600 million government contract to develop mRNA vaccines against avian flu and other high-risk strains.

Gluten sensitivity in people without celiac disease may be due to disruptions in the microbiome, the populations of healthy bacteria living in the intestines, a study in mice suggests.

Gluten is a protein found in wheat, barley, rye and other cereal grains. In celiac disease, the immune system reacts to gluten as a threat, leading to inflammation and damage to the small intestine and often to digestive symptoms as well.

Up to 15% of the population reports non-celiac gluten sensitivity, with digestive symptoms after consuming gluten but without harm to the gut, according to a report of the study published in the American Journal of Physiology-Gastrointestinal and Liver Physiology.

The affected individuals do, however, often have high levels of inflammatory cells, suggesting that gluten may be triggering an immune response.

When mice were treated with commonly used antibiotics that kill beneficial bacteria in the gut and then fed food containing gluten, the animals had shifts in the populations of bacteria living in their intestines that altered how the gluten was processed, which may influence how it is recognized by the immune system, the researchers said.

They also saw more inflammation and a heightened immune response to gluten after the antibiotic treatment.

“This work suggests that the microbiome may determine the capacity for gluten to induce an immune response and offers a valuable insight into the mechanism underlying non-celiac gluten sensitivity,” the researchers wrote.